New installation, hoping to do it safely this time.

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Offgridandlovingit
Offgridandlovingit Solar Expert Posts: 38 ✭
in Off Grid Solar & Battery Systems #1
Hi guys.

As some of you may or may not know, I am currently running a very small system completely off grid. I am very much aware that the way I am doing it is not correct. It works, but probably isn't the safest. What I would like to do is go through and basically redo it completely, but I need some advice on what I would need in order to do this. When I say that, I mean, what kind of safety devices (breakers, grounds, etc) and recommendations on a charge controller, inverter, etc.

I am looking at going with 1200w of solar at 24v. I am currently running about a quarter of that, so I know it will be more than enough for my power needs. To run a system that size, what charge controller would you recommend? Also, I know that connecting my current inverter to a breaker box would be nearly impossible to do safely, as it doesn't have hardwire AC out connections. Can you make a recommendation on an inverter capable of up to about 5kw surge that can be hardwired into a breaker box? That should be plenty of inverter, as my 2300w/4600w one is capable of running everything I am using at the moment. Expandability would be nice, but I am on a bit of a budget, and I know that this is enough power for me, so most likely I would look more at reducing consumption than expanding the system beyond that.

Any input that you guys have would be great. Thanks in advance.
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  • Offgridandlovingit
    Offgridandlovingit Solar Expert Posts: 38 ✭
    #2
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    Re: New installation, hoping to do it safely this time.

    Also, keep in mind that I am more of a hobbyist than a professional, so you may have to dumb things down a bit for me to understand exactly what you are describing. Sorry. I'm learning, but I know it isn't nearly as safe or effective as it could be currently.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: New installation, hoping to do it safely this time.

    Well we can certainly do some basic math.
    Since we don't know exactly what the panels are let's guess they are "GT panels" with a Vmp around 30. Even if not, with 1200 Watts MPPT tends to have an advantage. So you have to look at how much current you can expect: 1200 Watts * 77% efficiency / 24 Volts = 38.5 Amps. So a 45 Amp controller would be minimal. There's one of those: Morningstar Tristar 45 MPPT http://www.solar-electric.com/motr45ampmps.html
    At about $400 it's not too expensive, but $100 more buys a MidNite Classic Lite http://www.solar-electric.com/misoclli150m.html (also no meter) or an Outback FM60 http://www.solar-electric.com/oupofl60mpso.html (has meter). Something to consider.

    Budget alternate hardwire 3kW inverter could be a Samlex SA-3000K-124 http://www.solar-electric.com/sa3wa24vosiw.html Although you might not think of $1,200 as "budget". It has a 6kW surge rating. The 2kW model is about $400 less, but the surge rating is only 4kW.

    Wiring and circuit protection has to be determined after the major components are selected and the locations determined.
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  • Offgridandlovingit
    Offgridandlovingit Solar Expert Posts: 38 ✭
    #4
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    Re: New installation, hoping to do it safely this time.

    Whew. That's a really nice inverter, but you are right that $1200 is a bit more than I was hoping to spend. Would one like this one be reasonably effective as well? http://www.solar-electric.com/samlex-pure-sine-wave-inverter-pst-2000-24.html A bit weaker, but a bit more on par with my current budget. I am leaning toward that Outback FM60 for the controller. That would give me a little bit of room for expansion if need be, but still a manageable device budget-wise.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: New installation, hoping to do it safely this time.

    That is the 2kW one I mentioned with 4kW surge. Remember that neither of these has a built-in charger, so recharging the batteries when the sun doesn't shine becomes another issue. A stand-alone battery charger will add $200 to $250, but you're still below a unit with a built-in charger.
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  • Offgridandlovingit
    Offgridandlovingit Solar Expert Posts: 38 ✭
    #6
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    Re: New installation, hoping to do it safely this time.

    oh ok. Let's assume that I go with the outback fm60 and that 2kw inverter then. What else would I need? I know I need some kind of disconnects and fusing beyond just the ones that are built in to the inverter and controller, which I currently don't have. (told ya, not exactly the safest setup, but it is working) What should I be looking at for those?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: New installation, hoping to do it safely this time.

    From the roof down:

    Depending on how the array is configured you may need some circuit protection on each 'string' of panels. You may also want to put a breaker/disconnect on the whole array where it comes in to the charge controller.

    The controller's output should also have circuit protection on it. You will be running less than 60 Amps peak current, but there is no harm in sizing the wire and fuse/breaker to handle maximum capacity. The danger here is not from current generated by the array but from something shorting in the controller and the batteries back-feeding their enormous current capacity through the wiring.

    Likewise there would be another fuse/breaker between the battery bank and inverter. Again, wiring and CP sized to suit. A 2kW 24 Volt inverter draws around 84 Amps at maximum continuous output, so the circuit is usually designed to handle 100 Amps (the manual for the inverter should have manufacturer's recommendations which can't be beat).

    After that, the 120 VAC output of the inverter will have a 15 Amp breaker on each circuit. This is mainly for convenience, as in all likelihood the inverter will fault before one of those breakers trip.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
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    Re: New installation, hoping to do it safely this time.

    Also, if you have to meet code/inspection in your application you may have to make changes to comply with local authorities.
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  • Offgridandlovingit
    Offgridandlovingit Solar Expert Posts: 38 ✭
    #9
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    Re: New installation, hoping to do it safely this time.

    Awesome. That's exactly the information I was looking for. As far as meeting local codes, it's not really an issue where I am at, because I am so far back and away that no one will ever even know it is there unless I tell them. That being said, I will be checking just to make sure, but if this is a safe and effective setup, that's probably going to be plenty for me. Thank you so much.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #10
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    Re: New installation, hoping to do it safely this time.

    One might be back of beyond, but is your home insured? Here in Ontario any electrical work over 12vdc has to be inspected, even if it's off grid and off the beaten track. You can take the inspection certificate to your insurance comp[any in case of a fire (whether it's caused by the off grid work or not, and you know, if it's not been inspected that wil be the cause of your fire;)). You know insurance companies, if they can get out of paying your claim they will. Pointing to "unsafe, uninspected" electrical work would be mana for them. Just saying. It would be awful to have to rebuild without insurance company money if you had a fire.

    Ralph
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